Recognition of an irreducible explanatory role for reasons, and mental
properties generally, as expressed in the dual explananda
strategy, does not by itself fully do away with epiphenomenalist
concerns. In light of mental anomalism, why think that reason
explanations are causal explanations, rather than a sui
generis form of noncausal explanation? The need for a causal
relation between mental events cited in reason explanations (see
discussion of the ‘because’ problem in 2.2) doesn't settle
this issue once we have distinguished between causal relations and
explanations (see section 6). Neil
Campbell (1998 and 2005) argues for an interpretation of Anomalous
Monism on which while mental events stand in causal relations with
each other, reason explanations are not causal explanations. He calls
this ‘explanatory epiphenomenalism’. Causal explanations
explain because they fit singular causal occurrences into true causal
generalizations (2005, 442–43). However, reason explanations,
according to Campbell, are more plausibly thought of as functioning
along different lines: reasons explain actions by revealing the
agent's rationality in so acting in light of those reasons (2005,
445). The point of this explanatory epiphenomenalism is not to
criticize reason explanations as illusory—as wrongly claiming to
explain—but rather to point up limitations of the domain of
causal explanation. On this view, not all genuine explanations are
casual—reason explanations are sui generis and capture
a distinctive pattern in nature that would otherwise be missed. This
is an interesting twist on the noncausal theories of actions (2.2),
acknowledging both Davidson's criticism of them (the
‘because’ problem) in insisting on causal efficacy
(reasons cause (extensional) actions) yet also acknowledging their
disavowal of causal explanation as a model for reason explanation and
refusal to accept that only causal explanations capture real patterns
in nature. It also explicitly connects the distinctive feature of
reason explanation—rationality—to the reality of reasons
and mental properties generally
(see 4.3). Campbell is influenced
in this line of thinking by McDowell's reading of mental anomalism
(4.2.2), though he goes beyond
McDowell in denying that reason explanations are causal.

Campbell acknowledges that reasons which explain actions are backed
by generalizations (ceteris paribus ones), but claims that
this fact “takes a back seat” to the normative dimension of
rationalizing explanation, because generalizations record mere
tendencies while rational explanations observe what agents
should do—the fact that the generalizations hold is
explicable by rationality, something that is not true of other forms of
explanation (2005, 445). (Though Campbell doesn't argue this
explicitly, in this vein one might also point to the fact that the
truth of the generalizations does not—indeed, cannot—explain the fact that the relations covered are
rational. This is a key point in Kim's reconstruction of the
argument for mental anomalism—see 4.2.1.) The epistemic
satisfaction that reason explanations provide is achieved differently
than that of causal explanations—not by being an instance of a
generalization, but rather by being a realization of rationality.

By itself, this point does not appear to rule out the idea that
reasons explanations are causal explanations. Indeed, it seems to be a
non sequitur. First, in other cases where explanations covered
by generalizations are not thereby casual explanations—for
instance, logic—the obstacle has to do with not meeting basic
conditions for casual explanations, such as temporal succession. But
such conditions are met in reason explanations. Second, as we have seen
(4.2.1), Davidson emphasizes that a normative component also underlies
the physical realm in constitutive a priori principles. On
Campbell's reasoning, this would prevent physical explanations from
being casual, which is clearly wrong. We see once again a problematic
consequence of interpretations of the argument for mental anomalism
(Kim's and now Campbell's) that highlight a strong distinction between
normative and descriptive principles. Third, and related to this point,
reason explanations might be different than other causal explanations
in their subject matter without this preventing them from being causal.
After all, there are other causal explanations that are also backed
only by ceteris paribus generalizations, and a point analogous
to the one Campbell emphasizes—that their constitutive feature
explains why such generalizations hold rather than vice-versa—has also been made concerning biological explanations in particular and
functional explanations generally (Macdonalds 1995; for related
discussion, see below).

If rational explanations could be satisfying despite
failing to be instances of generalizations, then there might
be an asymmetry sufficiently strong to block the assimilation of
reasons explanations to causal explanations. But Campbell does not
argue for this, either in itself or as an interpretation of Davidson,
and it has no clear independent plausibility—the failure of a
reason explanation to generalize would in fact prevent it from being a
satisfying explanation (see also 4.2.3). Reason explanations are
satisfying both because they show that an action is a realization of
rationality and also because such explanations are instances
of generalizations. Both conditions are necessary for reasons
explanations, and cannot be pulled apart. None of this appears to be
inconsistent with reasons explanations being causal explanations, and
seems merely to individuate reason explanations from those that are
made relative to different explanatory interests.

However, Campbell provides an additional and conceptually distinct
point in favor of an asymmetry between the two that would block
assimilating reason explanations to causal explanations. Even though,
for example, hurricanes and catastrophes don't stand in strict lawlike
relations, the explanation of the latter by the former is causal
because we have at least a rough understanding of how hurricanes
function in terms of underlying mechanisms—the physical
properties co-instantiated by meteorological events. But the point of
mental anomalism is to deny that there can be any such understanding in
the case of reasons. Therefore, “without a means of connecting
reason explanations to their underlying causal processes in an
intelligible fashion there is nothing to account for their explanatory
force if such explanations are taken to be a species of casual
explanations” (Campbell 1998, 29). Campbell's point seems to be
that without an explanatory relationship between reason explanations
and the physical causal explanations underlying them, not only is there
no justification for holding reason explanations to be causal;
moreover, the problem of causal explanatory competition and exclusion
pressed by Kim (6.2) rears its head. Campbell's explanatory
epiphenomenalism is thus a form of the dual explananda
solution to Kim's problem, but one that further eschews explanatory
competition between reason and physical explanations by distinguishing
not only their distinct explanans and explananda but
also the form of explanation (causal or not) that relates them.

The Macdonalds (1995) hold, as Campbell does, that (1) mental events
are causally efficacious by virtue of being identical with physical
events, and that (2) despite the anomalous nature of reason
explanations, they capture distinctive patterns that account for their
explanatory usefulness. But the Macdonalds don't see this as
incompatible with reason explanations being causal. They cite
biological events and explanations as meeting (1) and (2)—the
pattern consisting in appearance of design resulting from natural
selection—but emphasize that these are nonetheless causal
explanations. It thus appears that the difference between their
attitudes is due to the second point raised by Campbell—whether
there exists an account of how such explanations explain. For
the Macdonalds, there is an underlying account of design and natural
selection in terms of underlying “physico-chemical
changes”. That suggests that for the Macdonalds there needs to be
an account of reason explanations in terms of the nomological
properties that mental events instance in order for reasons
explanations to be causal explanations—precisely what Campbell
claims is ruled out by Davidson's mental anomalism. And the Macdonalds,
who accept mental anomalism, indeed hold that the patterns in both
cases—rational and biological—must be “reliably
produced” by co-instanced nomological properties. However, and
crucially, such reliability does not depend upon or entail
exceptionless relations (see further below).

Campbell's explanatory epiphenomenalism is in effect calling into
question the Macdonalds' underlying assumption that patterns genuinely
occurring “in nature”—and thus real—must bear an explanatory relation to nomological properties. On
Campbell's view, that assumption is unwarranted, particularly given the
already established causal efficacy of mental events. Reason
explanations can pick out genuine patterns “in nature”
without being either causal explanations or explainable in terms of
underlying nomological properties. The relevance of this for the
current discussion is whether the Macdonalds' “reliable
production” requirement is consistent with Anomalous Monism,
which Campbell in effect denies. We have already seen (5.3) that the
Macdonalds endorse a supervenience relationship between mental and
physical properties, and claim that their conception of
supervenience is consistent with both the strict nature of
supervenience laws and also mental anomalism because we can't currently
state such laws and so are not in a position to predict or explain
mental events on their basis. As we have also seen, this is consistent
with—indeed, seems ultimately to require—a strict
explanatory/predictive relationship between physical and mental
properties, making mental anomalism into a merely epistemic and not
metaphysical thesis.

If one rejects this particular attempt to square supervenience with
mental anomalism, then the quagmire of 5.3 arises—how to
articulate a conception that provides for dependency without
exceptionless prediction or explanation. Interestingly, the Macdonalds'
later requirement of “reliable” (as opposed to
exceptionless) relations is suggestive of a ceteris paribus
conception of supervenience, which we earlier saw as an unexplored and
potentially fruitful direction to take in trying to square Anomalous
Monism with an explanatory priority of the physical through the
supervenience relation. (Campbell valiantly but implausibly tries to
fit Davidson's appeals to supervenience into Campbell's explanatory
epiphenomenalist framework by claiming that while reason explanations
depend upon physical causal explanations, this is a semantic and not a
metaphysical thesis (Campbell 1998, 37–38), and so presumably does not entail an
explanatory relationship between the mental and the physical of the
kind pressed by the Macdonalds. Much of what we have seen Davidson
saying about supervenience is inconsistent with this
interpretation.)

Since Campbell allows that reason explanations make actions
intelligible without falling under exceptionless generalizations
(mental anomalism), he can't object that physical properties cannot
make reasons intelligible simply because of an anomalous relation
between them. It might be responded that physical properties cannot
make reasons intelligible because “making intelligible”
means making rationally intelligible, and this is not
something that physical properties are in the business of providing (as
emphasized by the dual explananda approach). While this is
true, it is both questionbegging and misses the point. Explanations
always make phenomena intelligible within the terms of the
particular explanatory framework. This is the point of the idea
that explanation is interest-relative. Within the framework of
understanding the relationship between physical and mental properties,
ceteris paribus relations can make it intelligible why some
mental event is occurring—because some physical event is
occurring, and there is a ceteris paribus relationship between
them—even while not providing an exceptionless explanation
for its occurrence. Rational intelligibility is not the only kind of
intelligibility. As Campbell himself notes, the sort of explanation
that physical properties can provide for hurricanes is neither
exceptionless nor rational, but it nonetheless makes it intelligible
why a hurricane is occurring or how it is behaving within its own
particular explanatory framework.

The debate about asymmetries between reason and other explanations
does not end here, and though we cannot explore it any further, it is
worth briefly noting one direction in which it inevitably goes that is
close to the heart of Anomalous Monism. A plausible question to ask at
this point is why the generalizations—whether strict
or ceteris paribus—hold at the most basic level
between physical properties, between mental properties, and between the
two. In other words, why are the fundamental laws of our world as they
are? Now, an initial answer to this question might be that it is in
the nature of the properties related that the laws are what they are.
However, this answer masks an important asymmetry between the different
kinds of generalizations, emphasized by both Kim and McDowell
(4.2.1–4.2.2) and reflected in Campbell's discussion. In the case of
both purely physical and psychophysical generalizations, we can
conceive of the possibility of different relations holding. (Though
this point is powerfully intuitive, it is no simple task to make
precise. For relevant discussion, see Chalmers 1996, Mumford 2009 and
Latham 2011). This is the case whether the generalizations are strict
or ceteris paribus. In the case of psychophysical
generalizations in particular, there is no convincing answer
forthcoming to the question of why these mental properties supervene on
these rather than other physical properties. However, to the question
“Why are these actions explained by these reasons?”, there
is a deeper level of explanation available. And the answer isn't simply
“Because of a rational relation between the two”. Rather, it is because that
rational relation has no conceivable alternative. It is not
intelligible to us that those reasons might explain very different
kinds of actions. As we have seen, it isn't at all obvious that this
asymmetry entails that reason explanations are not causal explanations,
as Campbell insists. But there is no question that this asymmetry is
important to our understanding of Anomalous Monism and the nature and
status of reason explanations.

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